# How do nuclear properties influence the atomic properties and vice versa?

I was wondering how the nucleus can influence the atomic properties (chemical and physical). I found that the mass number influences the boiling, melting and density of an atom. Also the electron wave functions depend on the number of protons. But are there also other properties of the nucleus like electric or magnetic spin which influence the atomic properties? Or do some atomic properties influence the nuclear properties?

• The first that comes to mind is the hyperfine structure of the atom, that says that the energy levels of the electrons shift when taking into account the interaction between the nucleus and the electrons. – user137661 Jun 6 '19 at 21:44
• @SV There is even more than this, for example isotope shift (en.wikipedia.org/wiki/Isotopic_shift) in the spectral lines due to mass and volume difference of the nucleus. – eranreches Jun 6 '19 at 22:45
• @eranreches That looks very interesting, do you know if there is a book or article that shows how it is derived? – user137661 Jun 7 '19 at 1:23
• @SV You can consult "Atomic Physics" by C. J. Foot, section $6.2$. – eranreches Jun 7 '19 at 1:28

## 3 Answers

The OP is basically searching for hyperfine interaction. Nuclei may have magnetic dipole ($$I \geq) 1/2$$, electric quadrupole ($$I \geq) 1$$) and higher moments. These moments interact with the electrons and may cause hyperfine splitting of electronic energy levels. A famous example is the 21 cm line resonance due to the hyperfine interaction of the proton (S=1/2) and electron (S=1/2) spins in neutral hydrogen atoms.

Heavy nuclei exert a strong Coulomb attraction on the inner shell electrons. This force is so strong the first, lowest energy level electrons may come very close to the nucleus. The electrons energy is also dependent on the electron-electron interactions that occur in an atom. For heavy nuclei, the lower shell electrons actually have a non-zero probability of spending time inside a nucleus. This time inside a nucleus actually screens the electrons and increases the electron-electron energy. The solution can be derived using quantum mechanics.

• All s orbitals have an antinode in the centre of the atom, but because the volume of the nucleus is very small the probability of finding an s orbital electron in the nucleus is very small. See here, especially the top 2 sets of diagrams. Also see the 2D "drum" animations on Wikipedia. – PM 2Ring Jun 6 '19 at 23:18

It affect the chemical properties of an atom by changing its size and the wavefunctions of electrons,atom's electronegativity .